This invention relates to a key switch adapted to be used with a keyboard fitted to a computer, cash register, motorized typewriter and other electronic appliances.
The known key switch used with the above-mentioned various electronic appliances comprises the so-called mechanical type wherein a pair of fixed contacts are electrically connected together or shut off from each other by the selective operation of a movable contact unit, and the so-called capacitive type whose operation is controlled by the magnitude of capacitance stored between a pair of electrodes.
Obviously, these mechanical key switch and capacitive key switch have both merits and demerits. A keyboard fitted with either type of key switch has the drawbacks that its manufacture is time consuming, resulting in a high cost. For instance, a keyboard fitted with a mechanical key switch is handicapped by the fact that due to the specific construction of the mechanical switch, the keyboard substrate must be provided with a diode for each key switch. Fitting numerous diodes to the surface of the keyboard substrate consumes a great deal of time.
In contrast, a keyboard equipped with a capacitive key switch also has the defects that, when the keyboard substrate is provided with print wiring only on one side, the substrate should be provided with a jumper for each key switch in view of the specific structure of the capacitive key switch itself. In this case, too, the manufacture of a keyboard takes as long time as that of the type fitted with a mechanical key switch.
Referring to a keyboard provided with a capacitive key switch, it may be possible to omit the fitting of the above-mentioned jumper to the keyboard substrate, if print wiring in formed on both sides of the keyboard substrate. In such case, however, both sides of the keyboard substrate itself became noticeably expensive. Namely, both sides of the keyboard substrate have to be provided with numerous penetrating holes for the electrical connection of print wirings formed an both sides of the keyboard substrate. The machining of these penetrating holes also increases the cost of the keyboard substrate.
Consequently, regardless of which type of key switch may be used, the manufacture of the whole keyboard consumes a tremendously long time and presents difficulties in ensuring cost reduction.